Introduce ability to play mp4 files as they download

ts/util/getLocalAttachmentUrl.ts

@@ -1,15 +1,18 @@
 // Copyright 2024 Signal Messenger, LLC
 // SPDX-License-Identifier: AGPL-3.0-only
 
-import type { AttachmentType } from '../types/Attachment';
+import { isNumber } from 'lodash';
 import { strictAssert } from './assert';
 
+import type { AttachmentType } from '../types/Attachment';
+
 export enum AttachmentDisposition {
   Attachment = 'attachment',
-  Temporary = 'temporary',
-  Draft = 'draft',
-  Sticker = 'sticker',
   AvatarData = 'avatarData',
+  Draft = 'draft',
+  Download = 'download',
+  Sticker = 'sticker',
+  Temporary = 'temporary',
 }
 
 export type GetLocalAttachmentUrlOptionsType = Readonly<{
@@ -20,20 +23,41 @@ export function getLocalAttachmentUrl(
   attachment: Partial<
     Pick<
       AttachmentType,
-      'version' | 'path' | 'localKey' | 'size' | 'contentType'
+      | 'contentType'
+      | 'digest'
+      | 'downloadPath'
+      | 'incrementalMac'
+      | 'chunkSize'
+      | 'key'
+      | 'localKey'
+      | 'path'
+      | 'size'
+      | 'version'
     >
   >,
   {
     disposition = AttachmentDisposition.Attachment,
   }: GetLocalAttachmentUrlOptionsType = {}
 ): string {
-  strictAssert(attachment.path != null, 'Attachment must be downloaded first');
+  let { path } = attachment;
+
+  if (disposition === AttachmentDisposition.Download) {
+    strictAssert(
+      attachment.incrementalMac && attachment.chunkSize,
+      'To view downloads, must have incrementalMac/chunkSize'
+    );
+    path = attachment.downloadPath;
+  }
+
+  strictAssert(path != null, `${disposition} attachment was missing path`);
 
   // Fix Windows paths
-  const path = attachment.path.replace(/\\/g, '/');
+  path = path.replace(/\\/g, '/');
 
   let url: URL;
-  if (attachment.version !== 2) {
+  if (disposition === AttachmentDisposition.Download) {
+    url = new URL(`attachment://v2/${path}`);
+  } else if (attachment.version !== 2) {
     url = new URL(`attachment://v1/${path}`);
   } else {
     url = new URL(`attachment://v${attachment.version}/${path}`);
@@ -53,5 +77,32 @@ export function getLocalAttachmentUrl(
   if (disposition !== AttachmentDisposition.Attachment) {
     url.searchParams.set('disposition', disposition);
   }
+
+  if (disposition === AttachmentDisposition.Download) {
+    if (!attachment.key) {
+      throw new Error('getLocalAttachmentUrl: Missing attachment key!');
+    }
+    url.searchParams.set('key', attachment.key);
+
+    if (!attachment.digest) {
+      throw new Error('getLocalAttachmentUrl: Missing attachment digest!');
+    }
+    url.searchParams.set('digest', attachment.digest);
+
+    if (!attachment.incrementalMac) {
+      throw new Error(
+        'getLocalAttachmentUrl: Missing attachment incrementalMac!'
+      );
+    }
+    url.searchParams.set('incrementalMac', attachment.incrementalMac);
+
+    if (!isNumber(attachment.chunkSize)) {
+      throw new Error(
+        'getLocalAttachmentUrl: Missing attachment incrementalMac!'
+      );
+    }
+    url.searchParams.set('chunkSize', attachment.chunkSize.toString());
+  }
+
   return url.toString();
 }